Rome grew to dominate the world under the republic. After the republic fell, the emperors for the most part were content to simply defend what they had. But the tradition of conquest continued. Claudius added Britain and Dacia and Mesopotamia were conquered by Trajan. Several smaller scale campaigns outside the empire were undertaken too. So in 363 when Julian, the last pagan emperor led a Roman army drawn from all parts of the empire out across the border to conquer a foreign enemy he was doing something that was rare but which was not unprecedented. It would have broken his young and idealistic heart to know that this would be the last time the empire as he knew it would mount such an attack.

The force of 90,000 men he led into Persia was large by any standards and may well have been a third of the empire’s entire strength. It was sophisticated, well organised and well supplied. Julian himself was an experienced general with a strong track record, and there were other effective commanders on his staff. This was the kind of military expedition at which the Romans had historically excelled. It was an effective force with good prospects for success. But what exactly was its purpose?

Throughout history wars have been fought for many reasons. Sometimes, but rarely, the reasons have been good ones. But generally when you look closely most wars are fought for motives very different to what is claimed. Often it is simple. An external enemy is a perfect way to bolster the position of a weak regime. This seems pretty clearly to have been what was behind Julian’s attack on Persia. It wasn’t that his position on the throne was particularly precarious. In fact it was strong enough. He had the support of a large chunk of the army, and no obvious rivals. He might expect opposition from the mainstream Christians. But this wasn’t all Christians. The previously persecuted Christian sects had benefited from Julian’s edict of toleration. They were at the least not likely to want to overthrow him and risk getting persecuted again. He was strongly supported by the Jews and by the majority, the Pagans. So he was in no real danger.

But he was impatient to start rolling back the power of the Christians. And there was no better way to do this than by a successful campaign against the Persians. His Christian predecessor had been making heavy weather of fighting them. What better way to demonstrate the benefits of regaining the favour of the Gods than by a glorious victory that has cousin had failed to achieve. Julian would also be able to bind the eastern legions to himself in the same way he had already succeeded in doing with the western ones. With the army firmly behind him Julian would be sure to win if Christian dissent did break out into open civil war.

So the peace proposals from the Persian envoys representing Shapur, the King of Kings, were dismissed. It would be war, and war on a colossal scale. The barbarians in Germany were still in awe of Julian so there was no danger from that direction. The full power of the empire was available to defeat its biggest single enemy. And although diplomacy had been rejected, this didn’t mean political weapons were abandoned. They had with them a Persian prince of the blood called Hormisdas, who could be put forward as the Roman candidate for the throne. There wasn’t any particular issue with the legitimacy of the incumbent, but it didn’t do any harm to have one of his relatives to hand if the need arose. In fact Hormisdas had been at the Roman court from an early age and had become fully romanised. He was not just a figurehead but was reliable enough to actually lead some troops as well.

Julian moved to Antioch to supervise the preparations. The plan was to launch a three pronged attack with support on one of them from the Romans’ allies the Armenians. In the event the Armenian contribution was never to materialise. There was an issue here. Armenia had been the first Christian kingdom under the famous Tiridates and was still ruled by his descendents. The Armenian royal family were closely identified with the Christian cause and must have been alarmed by Julian’s pagan sympathies. It was probably not in their interest to support a campaign that was designed to promote paganism. Julian’s attitude towards the Armenians was haughty, but it may well have been his intention to stir up an argument with them. The Armenian regime can hardly have been one that Julian would have been keen on. The traditional Armenian culture had been eliminated by the Church. It was an example in miniature of what Julian was fighting against and a warning of the risk if he failed.

But militarily the betrayal by the Armenians should not have been hugely significant. There were still plenty of men to overrun the Persians. The biggest problem on the Roman side was logistics – feeding and supplying forces on the scale of this invasion was a massive undertaking. But the Romans had a long tradition of solving this kind of problem. One of the solutions was to build a huge fleet of 1,000 boats that could be used on the river Euphrates to supply the troops.

At first everything went pretty much according to plan. The Persians avoided battle since they had no hope of winning. The three columns advanced opposed only by the hostility of the terrain. One column was led by Julian himself who in the tradition of Julius Caesar and Alexander led from the front. He shared the hardships of his men – in fact the army was well supplied so there wasn’t too much hardship to share at first. But while Julian had laid on ample provisions he had banned wine. He wanted a well disciplined army and did everything he could to ensure it. He regularly spoke to the men, enforced strict punishments for misbehaviour and lavished donatives as well.

The Persians could not hope to win a battle, but opposed as they could. Rivers were diverted to flood the Roman camp. The Romans were delayed but not halted – their leader urging them on to great things. As they penetrated more deeply they started to encounter walled cities. Perisabor for example was a substantial stronghold, the second biggest city in the province of Assyria, and well armed and defended. But the ferocity of the Romans and their skill in siegecraft was legendary. Battering rams were deployed and the defenders overwhelmed as the legions stormed it.

It was impressive and eye-catching. And that was the point. Julian remarked that he was providing material for the sophist in Antioch. He referred to the great sophist of the age, Libanius. Libanius was a famous teacher of sophistry and rhetoric who had over the years established a reputation founded on his way with words. His insistence on maintaining his faith in the traditional religion had undermined his income but increased his prestige as a man of principle.

Needless to say, he was a favourite of Julian who must have had high hopes of the praise he could expect on his triumphant return. Julian was too intelligent to be duped by the empty flattery his position attracted. But justified acclaim from a man of courage, integrity and wisdom – that was worth having. In fact, I sometimes wonder if the desire to impress Libanius might have been the single biggest motive for the Persian campaign. Julian was a young man still eager for approval. It might well have been as simple as that.

It would also explain the rather theatrical behaviour of Julian as well. After the capture of Perisabor there was some moaning that the donative wasn’t enough for such a deadly battle. Julian addressed the issue head on.

“Riches are the object of your desires; those riches are in the hands of the Persians; and the spoils of this fruitful country are proposed as the prize of your valor and discipline. Believe me, the Roman republic, which formerly possessed such immense treasures, is now reduced to want and wretchedness once our princes have been persuaded, by weak and interested ministers, to purchase with gold the tranquillity of the Barbarians. The revenue is exhausted; the cities are ruined; the provinces are dispeopled. For myself, the only inheritance that I have received from my royal ancestors is a soul incapable of fear; and as long as I am convinced that every real advantage is seated in the mind, I shall not blush to acknowledge an honorable poverty, which, in the days of ancient virtue, was considered as the glory of Fabricius. That glory, and that virtue, may be your own, if you will listen to the voice of Heaven and of your leader. But if you will rashly persist, if you are determined to renew the shameful and mischievous examples of old seditions, proceed.

As it becomes an emperor who has filled the first rank among men, I am prepared to die, standing; and to despise a precarious life, which, every hour, may depend on an accidental fever. If I have been found unworthy of the command, there are now among you, (I speak it with pride and pleasure,) there are many chiefs whose merit and experience are equal to the conduct of the most important war. Such has been the temper of my reign, that I can retire, without regret, and without apprehension, to the obscurity of a private station”

The resignation threat showed that he was confident of his position, but it also comes across as a bit melodramatic. Or was the whole episode a photo opportunity artfully managed to project the image Julian wanted to the audience back home. We’d call it spin nowadays. But you can be a self publicist and still be a hero. Julian was leading his army into enemy territory, and even if they were being done for show his military achievements were still real.

The army marched deeper into the Persian empire. There were more cities to be taken. And the logistics of the operation were formidable, with the army being supplied from a fleet of boats sailing down the Euphrates in step with them. All the obstacles were overcome. All resistance was beaten down. Until, in the middle of May they arrived at the capital. The Persians attempted to prevent Julian reaching the city, but in pitched battle outside the Romans defeated them. Julian could now lay siege to Ctesiphon itself.

Interesting juxtaposition of Julian and Napoleon. I'm not sure there are significant parallels to be drawn, but thinking about what they had in common gave me something to do while I was weeding the garden.